When using bridge cranes it is a practice to suspend them from two or more parallel runway rails. This is accomplished by constructing the bridge crane in a rigid I-shaped pattern. At the points of the I are pairs of carrier heads which hang from the runway rails and are rigidly connected to one another by side beams. Each side beam is in turn rigidly connected to the other by a bridge beam on which is hung a trolley for supporting a load. The carrier heads all have flanges on the wheels or side thrust rollers designed to keep the wheel on the runway rails. This I-shaped structure runs well so long as the rails are correctly hung. In practice, however, it is practically impossible to align the runway stands exactly parallel. Thus there are created variations in the distance between the runway stands. Normally the variation can be kept to a point where the trolley will travel on this runway stand without binding. The variations create pressure against the members designed to keep the carrier heads on the rails and lead to their early failure. Since the bridge cranes are suspended large distances above the floor, the maintenance cost of frequent replacement becomes significant. In addition lost production time results whenever such replacement is required. The invention allows the trolley assembly to remain in line with the runway rails without side pressures, despite deviations from a parallel relationship of those rails.